Dam failure and mammals

Brazil experienced the largest socioenvironmental catastrophe of its history, caused by a tailings dam failure, known as “Mariana disaster”. The wave of iron-mining waste buried villages, contaminated the Doce River, and left an immense ocean plume. The Doce River watershed is the largest in southeast Brazil, and located in the Atlantic Forest domain, presenting an outstanding economic, social, and biological relevance. Although the effects of such tragic events are usually assessed through fish assemblage changes, mammals have important effects on environment structure and regeneration. Inventories are of prime importance for adequate conservation efforts as well as for evaluating impacts of any disaster. Therefore, the aim of this paper was to present an updated assessment of mammalian list collected in the affected portion of Doce River before the dam failure therefore contributing to future conservation efforts. Data collection comprised specimens deposited in Museu Nacional/UFRJ, the oldest mammal collection of Brazil, and literature review. The two surveys together retrieved 157 species from 31 families and 11 orders, representing around 60% of the known mammalian diversity in the Atlantic Forest, including some in critical conservation condition, such as the Franciscana dolphin, the northern muriqui and the giant otter. Mining is a byproduct of present society, with dam breaches as a recurring problem. Facing the importance of Doce River to both Brazilian biodiversity and society, the chain of events must be taken into account in environmental rehabilitation strategies, and taxa less commonly assessed, like mammals, should be included.

Reactive improvement of environmental policies: lessons from the Mariana and Brumadinho disasters

The State is not always able to proactively improve environmental policies. Eventually, policy improvements are a result of disasters that expose pre-existing problems. This situation is reflected in the state of Minas Gerais (Brazil), where, after the failures of the Fundão and B1 tailings dam, in Mariana and Brumadinho, several problems in dam safety and emergency policies were exposed. This study had a twofold objective: 1) to identify the mechanisms used by the government of Minas Gerais to improve environmental policies, and 2) to understand how the Mariana and Brumadinho’s disasters affected dam safety and emergency policies. Based on semi-structured interviews and regulatory analysis, the study revealed that the state government of Minas Gerais has been predominantly reactive in controlling environmental policies. Additionally, it was observed that the disasters catalysed a learning process that culminated in potentially better dam safety policies.

Tailings Dam Break: The Influence of Slurry with Different Concentrations Downstream

The risk of tailings dam-break disaster is dependent on the type of slurry and its flow characteristics. The flow characteristics of slurry surging from tailings dams collapse are directly influenced by grain size, breach width, slurry concentration, and surface roughness of the gully. Among these parameters, slurry concentration plays the most critical role, but there are few studies on it. This paper focuses on the flow characteristics of slurry with different concentrations, and a series of flume experiments were carried out to obtain the flow characteristics of inundated height, impact force, and velocity in 30%, 40%, 50%, and 60% concentrations. The study confirms that the concentration of slurry has a significant influence on the flow characteristics. Through the experimental study, it is observed that, with the decreasing of slurry concentration, the impact force and velocity of slurry increased in varying degrees; on the contrary, the flow height elevated with the slurry concentration decreasing. The main reason is that the higher the slurry concentration, the higher the static yield stress and viscosity—in varying degrees. The results can provide a detailed understanding of the slurry concentration influence on the flow characteristics, which guides the evacuation time and height downstream.

Tailings Dam Conceptual Design with Geomechanical Material Properties Approach to Determine Safety Criteria

Geotechnical conditions as one of the conditions considered in the design and planning of tailings dams are strongly influenced by material conditions. The material condition is a parameter that will always be taken into account with stability. The material condition can be defined as a behavior that is based on the physical and mechanical properties of the material. By understanding the behavior of materials in a tailings dam construction, the risk of geotechnical failure can be controlled and minimized. This research was intended to study and investigate the behavior of material based on the geomechanical properties of the material used in a model. Generally, to determine the geomechanical properties of a material, several tests, both in-situ and laboratory tests, are required. Laboratory testing uses international standards such as ISRM (International Society of Rock Mechanics) and ASTM (American Standard Testing Materials). The research methodology used is descriptive quantitative research method. The studied parameter in this research is the geomechanical properties that influence the material on its conceptual design in terms of safety criteria (safety factor and probability of landslides) on the tailings dam embankment.

Combination of ground penetrating radar and seismic surveys of the tailings dam

Identification of water-saturated zones in the tailings dams is an actual scientific and practical task in terms of providing, first of all, their mechanical strength and filtration stability. Use of active sounding geophysical study methods allows obtaining sufficiently detailed information about the peculiarities of the internal structure of the tailings dam and the degree of water saturation of the composing soils. The paper presents the results of in-situ experiments on the study of the tailings dam of the mining enterprise by ground penetrating radar (GPR) and seismic methods. A comparative analysis of the conducted studies has allowed clarifying the internal structure and assessing the dam’s condition, paying special attention to the identification of local zones of increased water saturation and filtration. Based on the calculated correlation coefficient of electromagnetic and seismic wave velocity values, it was revealed that synchronization of geophysical surveys allows significantly increasing the reliability of in-situ determinations, as well as obtaining more reliable data. The results of the studies are the basis for predicting the most vulnerable places (zones) of a bulk ground hydraulic facility, as well as the localization of water-saturated areas in the body of the ground structures with greater reliability and performance.